The invention relates to a corner area of a sealing structure for tunnel tubing segments. The ends of two sides of the sealing structure meet at an angle. The sealing structure consists of sealing profile strips and a corner piece joining the ends of these strips. The sealing profile strips are provided, in cross-section, with grooves and cavities running continuously along their length and into the ends.
Tunnel tubing segments are typically rectangular, often slightly curved plates of concrete for lining excavated tunnels. In order to prevent water seepage from dripping into the tunnel, each tubing segment has along its four narrow sides or edges a continuous groove into which a sealing profile strip, which protrudes somewhat from it, is inserted. The tubing segments are installed under pressure such that they touch each other along common sides or edges. Thus, the sealing structures come to lie against each other side by side under high pressure, and are pressed completely into the tubing segment continuous groove. In the tunnel, they form a real sealing network which extends both over the arch of the tunnel and along the length of the tunnel. The sealing profile strips themselves are prefabricated industrially, by extrusion in any suitable length. They are then cut to the size which corresponds to the length of the sides of the tubing segments.
The cross-section of the continuous grooves in the tubing segment and that of the sealing profile strips, as well as the characteristics of their rubber material, must be carefully coordinated since conflicting conditions must be addressed in order to seal the tunnel perfectly. Thus, it is first necessary to take into account the fact that rubber, while readily deformable, is virtually incompressible, contrary to widely held opinion. The entire volume of rubber can be reduced only insignificantly under pressure. Consequently, the sealing profile strips must be provided with cavities disposed in their interior, which cavities can be deformed during installation under pressure in order to be able to force the profile strips into the continuous grooves. This is also important because, with the alignment of the tubing segments against each other, tolerances in the dimensions must constantly be taken into account.
There are still other conditions to consider. In order to accommodate the greatest possible tolerances, the sealing structure cross-section must be relatively large. The tubing segment continuous groove is, however, more susceptible to damage the larger it is. The continuous groove should thus be kept as small as possible. To achieve high leak resistance, relatively high sealing pressures are essential, and these are achieved better with a large cross-section of the sealing profile strip. On the other hand, due to cost considerations, a sealing structure cross-section as small as possible is preferable.
For this reason, the cross-section of the sealing profile strip and the cross-section of the continuous groove in the tubing segment are coordinated such that an optimally matched and shaped sealing profile strip cross-section can be deformed into as small a continuous groove cross-section as possible.
If the sealing profile strip cross-section is larger than the smallest possible continuous groove cross-section taking all possible tolerances into account, with the pressing of the tubing segments--which sometimes involves quite significant forces, it is possible that the edges or flanks of the continuous groove of the tubing segment may burst.
All of these conditions have an effect on the corner area of the sealing structure which is cut from the individual pieces of the extruded profile strip. The corner areas are produced by insertion of the pieces into a mold and subsequent injection of unvulcanized rubber into the empty corners of the mold. The rubber is vulcanized here by pressure and heat. Consequently, the design of the corner areas must be given special consideration with regard to the aforementioned conditions. This is easiest if the sealing profile strip has a curved cross-section but no cavities. Then this cross-section remains unchanged even at the corners. This is not the case with sealing profile strips with cavities or heavily undercut areas, since inserts applied in the cavity area cannot be removed after vulcanization and only with great difficulty with undercuts.
With the same cross-section in the corner area and sealing profile strip, there is deformation during the assembly in the corner area resulting in an enlargement of the cross-section since both ends of the sealing profile strip are compressed in the lengthwise direction thereof. This is expressed in an expansion of the cross-section. This effect becomes even greater if the material cross-section in the corner area is already enlarged by the production process.
Consequently, a solution must be found which makes it possible to reduce the material cross-section in the corner area so much that here as well, as in the area of the sealing profile strip, the material cross-section is not larger than the space available here defined by the cross-section of the joint. A larger material cross-section results here as well in a bursting effect, which causes the weaker joint flanks of the tubing segment to chip off.
According to the French Published Application No. 2,655,573, the proposal is made to reduce this material accumulation in the corner by making the profile strips smaller. This could be done on only one side of the corner, or on both sides meeting in the corner. Aside from the fact that, in the latter case, the pressing together of the two adjacent strips is virtually inevitable in the wedge-shaped opening thus formed, this type of material reduction has the disadvantage that the tolerance range in the direction of the width of the joint essential for compensation for imprecisions in assembly is reduced by the decreased depth of the profile.
The invention attempts to avoid these disadvantages and also takes into account the conditions mentioned above.